Unfortunately I think this is just a problem with Forge ATM. Its seems like too much of a coincidence that the last post on this was almost a year ago, and as soon as i start having problems, someone else posts here. I havent been able to download the Libraries with this same exact issue.
Actually it looks like Amazons Web Hosting is having some issues, that could be part of the problem. Heres the Story https://techcrunch.com/2017/02/28/amazon-aws-s3-outage-is-breaking-things-for-a-lot-of-websites-and-apps/